Present current-measuring devices are clamp-around devices which employ magnetic cores having arms that wrap around or clamp onto a current-carrying wire. The current in the wire or conductor (whose current is to be measured) induces a magnetic flux in the core of the clamp-around device which varies with the magnitude of the current flowing in the conductor. Coils wound upon the core respond to the induced magnetic flux and produce a current that is used to deflect a galvanometer needle which indicates the magnitude of the current flowing in the wire or conductor.
These clamp-around type current-measuring devices have disadvantages, however, which limit their applications. For example, the two arms of the clamp-around core normally must touch each other and therefore can not be used where the current-carrying conductor is disposed in tight locations which prevent the arms of the core from encircling such current-carrying conductor. And, of course, these clamp-around type current-measuring devices cannot be used for printed circuits such as are used on printed circuit boards since, in such case, there are no wires or conductors to encircle. Also, these clamp-around type current-measuring devices are normally capable of determining only one unknown variable which is the magnitude of the current flowing in the current-carrying conductor. These clamp-around type current-measuring devices are not capable of determining their linear distance relative to the current-carrying conductor.